Add Civ Lite combat feedback

[YfengJ]

Closes #23.

Summary

• adds a tested feedback model for floating combat text and screen shake decay
• shows damage labels, KO callouts, stronger hit particles, and capture feedback in the Civ Lite canvas
• applies subtle screen shake during combat/capture while preserving the existing movement tween and render loop

Validation

• find demo/civ-lite -name '*.test.mjs' -print | sort | xargs node --test\n- node --check demo/civ-lite/feedback-model.js && node --check demo/civ-lite/game.js && node --check demo/civ-lite/sprites.js\n- git diff --check\n- Chrome/Playwright smoke against demo/civ-lite/index.html: canvas rendered nonblank, no page errors, all app resources loaded

[YfengJ]

CI note: SonarCloud passed with 0 new issues. The only red check is the existing Godot Web export preset configuration failure (Cannot export project with preset "Web" due to configuration errors), which is unrelated to this Civ Lite JS feedback change.

Local validation completed:

• find demo/civ-lite -name '*.test.mjs' -print | sort | xargs node --test\n- node --check demo/civ-lite/feedback-model.js && node --check demo/civ-lite/game.js && node --check demo/civ-lite/sprites.js\n- git diff --check\n- Chrome/Playwright smoke: page loaded, canvas rendered nonblank, app resources loaded

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud